1,577 research outputs found
Dynamics of the vortex line density in superfluid counterflow turbulence
Describing superfluid turbulence at intermediate scales between the
inter-vortex distance and the macroscale requires an acceptable equation of
motion for the density of quantized vortex lines . The closure of such
an equation for superfluid inhomogeneous flows requires additional inputs
besides and the normal and superfluid velocity fields. In this paper
we offer a minimal closure using one additional anisotropy parameter .
Using the example of counterflow superfluid turbulence we derive two coupled
closure equations for the vortex line density and the anisotropy parameter
with an input of the normal and superfluid velocity fields. The
various closure assumptions and the predictions of the resulting theory are
tested against numerical simulations.Comment: 7 pages, 5 figure
Thermodynamics and kinetics of solids fragmentation at severe plastic deformation
The approach of nonequilibrium evolution thermodynamics earlier offered is
developed. It helps to describe the processes of defect formation within the
adiabatic approximation. The basic equations system depends on the initial
defects distribution (dislocations and grain boundaries). The phase diagram is
determined with the domains of the realization of different limiting structure
types. The interaction effect of several defect types on the formation of a
limiting structure is investigated in terms of the internal energy. The
conditions of the formation of two limiting structures are found. The kinetics
of the steady-state values establishment of the defects density is investigated
within the scope of the adiabatic approximation. The dislocations density
change follows the evolution of the grain boundaries density in this approach.
It is shown that grain sizes, in limiting structures, decrease with an increase
of the elastic strains.Comment: 14 pages, 6 figure
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